The Martial Arts is comprised of different elements, some are: conditioning, coordination, better circulatory flow ( greater capacity of oxygen in the blood), development of the "will", and overall...
One learns martial arts by one going to lessons...
At a martial arts school. Japanese martial arts are taught in a dojo.
Mexican Judo
Technically they use Ninjustu (The Art of Stealth) but in some circumstances they use Taijutsu (Body Skill or unarmed combat).